1. Field of the Invention
The present invention is related to a flow regulating device which controls the flow amount of a liquid chemical or pure water or the like, and is related to Patent Application No. 2002-328116, filed Nov. 12, 2002, the content of which is incorporated herein by reference.
2. Description of Related Art
FIG. 4 is a sectional figure which shows an example of the construction of a prior art type flow regulating device. This type of flow regulating device 1 is one which is used in a supply line for the flow of a fluid, when mixing together a plurality of different liquid chemicals, or when accurately regulating the flow amount of pure water or the like which is to be used for a manufacturing process for a product. Furthermore, a flow regulating device 1 which is used for this sort of application is also sometimes generally termed a“regulator”.
The structure of this flow regulating device 1 will now be explained concretely. Its housing, which presents its external aspect, is made from a material such as resin or the like, and it comprises a fluid intake port 21 and a fluid outlet port 24 which are formed upon its exterior. Furthermore, in the interior of this housing 10, as main components, there are provided a valve seat 11 which comprises an opening surface 11a which is communicated to the intake port 21, a valve element 30 which shifts in the vertical direction with respect to this opening surface 11a of the valve seat 11 (the upwards and downwards direction in the figure), a diaphragm 35 which is fixed on the upper surface of this valve element 30, and a spring 36 which presses the valve element 30 towards the valve seat 11. It should be understood that it is per se conventional to make this valve element 30 as two members, as shown in the figure.
Furthermore, the flow conduit in which the fluid flow is taking place is made up from a first plenum 22 which connects from the intake port 21 to the valve element 30 (generally this is termed the “valve chamber”), and a second plenum 23 which is positioned between the valve seat 11 and the diaphragm 35 and connects to the outlet port 24.
In addition, a closed pressure chamber 12 is defined on the other side of the diaphragm 35 from the second plenum 23, in other words on the upper side of the diaphragm 35 as seen in the figure, and this pressure chamber 12 is communicated with a pressure inflow port 13 which is formed in the upper portion of the housing 10.
The structure incidental to the valve element 30, and the operation of the valve element 30, will now be explained.
By the lower portion of the outer peripheral portion of the valve element 30, which is its end portion, being inserted in a valve element insertion groove 25 which is formed in the housing 10, the valve element 30 can shift in the upwards and downwards direction in the drawing along an axial line which is perpendicular. Furthermore, this valve element 30 is pressed from downwards in the upwards direction by a spring 36 which is provided below it, within the valve element insertion groove 25. In other words, by pressing the valve element 30 against the valve seat 11, this spring fulfills the function of closing the valve seat 11.
On the upper portion of the valve element 30, there is formed a projecting spiral screw portion 30a, and the valve element 30 and the diaphragm 35 are mutually fixed together by this projecting spiral screw portion 30a being screwed into a spiral screw portion which is formed in the diaphragm 35. It should be understood that, according to the particular structure, the valve element 30 and the diaphragm 35 may not be fixed together.
Furthermore, when air or the like is supplied from the pressure inflow port 13, the pressure chamber 12 is pressurized, and the diaphragm 35 experiences a force which overcomes the elastic force of the spring 36, so that the diaphragm 35 is pressed downwards. Due to this, the valve element 30 which is fixed to the diaphragm 35 is removed from the valve seat 11 and the opening surface 11 a of the valve seat 11 is opened, so that the fluid which has filled up the first plenum 22 flows into the second plenum 23. Since at this time the shifting distance in the upwards and downwards direction of the valve element 30 varies according to the degree of pressurization of the pressure chamber 12, the flow amount of fluid which passes through the opening surface 11a of the valve seat 11 comes to be regulated thereby. In addition, by the flow amount which has flowed into the second plenum 23 flows toward the outlet port 25 and being ejected therefrom, it becomes possible to perform the regulation of the flow amount of fluid which passes through the flow regulating device 1.
The flow regulating device 1 of this type of structure is one which has been disclosed in various published prior arts; some of these are ones in which, instead of the above described air which causes the position variation of the diaphragm 35, there is provided a flow regulation mechanism of a needle type, in which a diaphragm is pressed inwards by a screw (for example, refer to Japanese Patent Application, First Publication No. Hei 6-201063).
This type of flow regulating device 1 may be provided in a circuit and may fulfill the function of performing flow amount regulation of, for example, the flow of a liquid chemical, or of pure water for the manufacture of semiconductor devices or the like. As a result, deviation can arise in such flow amount regulation, due to variation over a short time period of the temperature of the fluid whose flow amount is to be regulated, or due to variation of the temperature of the external environment. This can cause the result that the temperature range over which it is possible to perform accurate flow amount regulation may be severely limited.
Furthermore, the flow conduit in which the above described type of flow regulating device is provided, and which is adapted for the flow of a liquid chemical, may be formed by a resin material such as a fluorinated resin which has excellent chemical resistance and provided in the housing. However, since this type of resin material has a rather great amount of heat deformation as compared to metallic materials of the flow regulating device, it can sometimes happen that, due to deviation occurring at the sealing surface of the flow conduit, the sealing structure may be destroyed. This may be caused because the temperature distribution at the various portions of the housing is different.
By a sealing surface here is meant the sealing surface between the inner wall of the housing 10 and the diaphragm 35 shown in FIG. 4, or a sealing portion K which constitutes a sealing construction and including a stepped portion having a sealing surface or the like at each of several portions which make up the housing 10, or an O ring, or the like; and, when change of shape takes place in this type of portion due to heat deformation, there is a possibility of the sealing construction being destroyed, of the pressure reducing, and of leakage of the fluid.
Furthermore, as well, with regard to the valve element insertion groove 25 which is formed below the valve element 30 and which governs the operating direction of the valve element 30, it may also be predicted that it may be deformed by change of the temperature of the flowing fluid in the same manner as described above, by change of the temperature of the external environment, or by rise of temperature or abrasion due to friction with the valve element 30. In such a case, a gap may appear between the inner peripheral surface of the valve element insertion groove 25 and the outer peripheral surface of the valve element 30, and, not only the problem may arise that the groove direction of the valve element insertion groove 25 may become tilted with respect to the perpendicular direction, or the like, but a problem may arise in the smooth shifting of the valve element 30 along the perpendicular axial direction, so that it may become impossible to maintain the opening amount of the valve seat 11 fixed in accordance with the value to which the flow amount is to be regulated.
The present invention has been conceived in the light of the above described situation, and its objective is to provide a flow regulating device which is capable of performing accurate flow amount regulation over a wide range of temperature, while maintaining the qualities of excellent chemical resistance by utilizing a flow conduit which is formed in a housing which is made from a resin material.